1. Field of the Invention
This invention relates to a novel herbicidal composition for use in paddy fields.
2. Description of the Prior Art
Among existing herbicides used in transplanted paddy fields, pentachlorophenol, diphenyl ethers, etc. are well known for their excellent herbicidal effects when applied at the initial stage of growth of weeds. On the other hand, DCPA and SWEP.M (a mixture containing 20% of methyl-N-(3,4-dichlorophenyl) carbamate and 0.7% of ethyl 2-methyl-4-chlorophenoxy acetate) are also used as a herbicide but they are applied after the weeds have grown to some extent. DCPA, however, requires drainage of water completely from the paddy fields before its application. If the draining is insufficient, DCPA fails to give satisfactory weeding effects. In this connection, it is practically extremely difficult to drain water completely from paddy fields, so that DCPA is rarely employed in practical application. SWEP.M may be used in fields filled with water, but its herbicidal effects and phytotoxicity on rice plants vary considerably depending on particular temperatures and soil conditions, i.e., the herbicidal activities of the agent are reduced under low temperature conditions while the adverse effects of the agent become pronounced under high temperature conditions. Furthermore, in the paddy fields with continued leaching of water, the agent penetrates into the soil and is absorbed by roots of the rice plants, causing damage to the rice plants.
In addition, when SWEP.M is used in combination with carbamate or organic phosphorous base insecticides, a great problem occurs in practical applications in that rice plants are seriously damaged. Accordingly, it is strongly desired to develop a novel herbicide which has stable effects in removing weeds which have grown to a certain degree, without resulting in phytotoxicity to the rice plants.